The aim of this study was to investigate the direct effect of leptin on GH gene expression and secretion and the role of nitric oxide as a possible mediator in pig anterior pituitary cells. Pituitary cells from adult sows were treated for 4 or 24 h with rhleptin (from 0.1 nM to 1 microM) alone or in association with GHRH (10 nM) or hexarelin (10 nM). At the end of incubation, medium was collected for GH and nitric oxide determination by ELISA and Griess test, respectively. Total RNA was collected from cells, and GH gene expression was measured by RT-PCR. Leptin significantly (P < 0.001) stimulated GH secretion in both incubation periods. The maximum response was induced by 10 nM leptin; furthermore, a significant interaction (P < 0.002) between leptin and GHRH (P < 0.03) and between leptin and hexarelin was observed when the molecules were used in association. GH gene expression was significantly increased (at least P < 0.05) by hexarelin, GHRH, and leptin (1000 and 100 nM) after 24 h of treatment. Leptin (10 nM and 1 microM) significantly (P < 0.05) increased nitric oxide production, whereas S-nitroso-N-acetyl-penicillamine (from 0.01-1000 nM) significantly (P < 0.05) stimulated GH secretion. These data demonstrate that leptin directly influences GH regulation at the pituitary level, and nitric oxide may be involved in this function.
Objective: We studied the effects of IL-1β, IL-6 and TNF-α on GH gene expression and secretion with or without galanin and hexarelin. Methods: Pituitary cells from adult pigs were treated with IL-1β, IL-6 or TNF-α (1, 10 and 100 ng/ml), alone or in association with galanin or hexarelin (10–8M): GH mRNA was measured by RT-PCR and GH secretion by ELISA. Results: IL-1β (1, 10 and 100 ng/ml) and IL-6 (1 and 10 ng/ml) significantly (p < 0.05) enhanced GH output. IL-1β and TNF-α (1 and 10 ng/ml) reduced (p < 0.05) the galanin-induced GH secretion and IL-6 (10 ng/ml) potentiated the effect of both GH releasers (p < 0.05). GH gene expression was increased only by IL-6 at the concentrations of 1 and 10 ng/ml, either alone or in association with both galanin and hexarelin. Conclusions: We hypothesize that cytokines may play a paracrine/autocrine role in GH regulation in the pituitary independently from the intracellular pathways of the GH secretagogues.
This study was designed to investigate the presence of bioactive tumour necrosis factor-alpha (TNF-alpha) in bovine fluid collected from small (<5 mm) and large (>8 mm) follicles, as well as the production of the cytokine by the granulosa cells collected from the same type of follicles. Moreover, the effectiveness of 10, 1 and 0.1 ng mL(-1) of human TNF-alpha (hTNF-alpha) in affecting the main parameters of granulosa cell function, progesterone (P4) and oestradiol-17beta (E2) production, cell proliferation and apoptosis, was tested. In addition, the study aimed to determine whether the signalling mechanisms of TNF-alpha in these cells involve cAMP, nitric oxide or prostaglandin E2 (PGE2) and F2alpha (PGF2alpha). It emerged that bioactive TNF-alpha is present in follicular fluid from both types of follicles and can be measured in media conditioned by granulosa cells from large follicles. As for the effects of hTNF-alpha, it inhibits P4 production in cells from both types of follicles and stimulates E2 output in those from small follicles; it does not affect proliferation, but it stimulates granulosa cell apoptosis. Finally, the effects of hTNF-alpha on bovine granulosa cells are not mediated by nitric oxide or cAMP, as neither of these substances were affected by treatment with the cytokine; however, in some way, they could be mediated through PGE2 and PGF2alpha, the production of which was inhibited by TNF-alpha in cells from small follicles.
-In this study we investigated the somatotropic axis in piglets with evident growth delay. Female Suffolk crossbred piglets (30 days old; N = 12) were divided into normal weight (10 ± 0.9 kg) and poor growing subjects (7 ± 0.5 kg) and bled for growth hormone (GH), Insulin-like growth factor-I (IGF-I), Insulin-like growth factor binding protein 2 and 3 (IGFBP-2 and -3) determination. Basal and induced-GH levels were not different in the groups. Plasma IGF-I concentrations were significantly different (p < 0.001): 101.8 ± 9.8 ng . mL -1 (normal weight group) and 39.5 ± 4.0 ng . mL -1 (poor growing group). IGFBP-2 and -3 concentrations were significantly (p < 0.001) lower in poor growing than in normal piglets. Piglet weight was positively correlated (r = 0.98, p < 0.001) with IGF-I and IGFBP-2 or -3 concentrations. Our data indicate that growth rate was not correlated to basal or secretagogue-induced GH secretion. growth hormone / somatotropic axis / insulin-like growth factor I / insulin-like growth factor binding protein / pigletRésumé -Les concentrations de IGF-I, IGFBP-2 et -3 sont différentes chez les porcelets normaux et chez les porcelets qui présentent un retard de croissance ; cette différence n'existe pas pour la GH. L'objet de cette étude est l'axe somatotrope chez les porcelets présentant un retard de croissance manifeste. Douze porcelets femelles croisés Suffolk (âgés de 30 jours) ont été subdivisés en deux groupes : sujets de poids normal (10 ± 0,9 kg ; N = 6) et sujets avec retard de croissance (7 ± 0,5 kg ; N = 6) : des prélèvement sanguins ont été effectués pour la détermination de l'hormone de croissance (GH), de l'Insulin-like growth factor I (IGF-I), et des Insulin-like growth factor binding protein-2 et -3 (IGFBP-2 et -3). Aucune différence n'a été observée entre les concentrations basale et induite
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